Circuit-interrupter.



K. C. RANDALL.

CIRCUIT INTERRUPIER. APPLICATION FILED JUNE 9,1914.

1,229,789. Patented June 12 1917.

WITNESSES INVENTOR /mmm/ ATTORNEY UNITED STATES PATENT OFFICE.

KARL C. RANDALL, OF EDGEWOOD PARK, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC AND MANUFACTURING COMPANY, A. CORPORATION OF PENNSYL- VANIA.

CIRCUIT-INTERRUP'I'ER.

Specification of Letters Patent.

Patented June 12,1917.

To all whom it may concern:

Be-it known that I, KARL C. RANDALL, a citizen of the United States, and a resident of Edgewood Park, in the county of Allegheny and-State of Pennsylvania, have'invented a new and useful Improvement in Circuit-Interrupters, of which the following is a specification.

My invention relates to circuit interrupters and particularly to means for adapting the same for parallel operation.

The object of my invention is to provide means for equalizing the currents traversing circuit interrupters which are connected in parallel relation.

The advent of large generating stations has increased the demand for adequate switching equipment of large current-carrying capacities. It has been proposed to employ circuit interrupte rsof standard sizes for interrupting relatively large currents and to connect a plurality of such devices electrically in parallel and to connect them together mechanically for simultaneous operation. However, it is impracticable to construct two circuit interrupters which will have so nearly the same characteristics that they, will divide the current equally without providing automatic means for this purpose, unequal division of the current becoming manifest, when the circuit interrupter is tripped, by the fusing or overheating of the contact members connected in one of the parallel circuits:

I provide electromagnetic means for equalizing the currents in all branches of a parallel-connected circuit interrupter, so that, if one branch tends to transmit more current than the other branch or branches, increased voltages will be induced in the latter which are sufficient to equalize the current traversing the difierent branches.

Figure 1 of the accompanying drawings is a side view, partially in elevation and partially in section, of a circuit interrupter embodying my invention. Fig. 2 is a fragmentary front elevational view of the circuit interrupter shown in Fig. 1. Fig. 3 is a fragmentary top plan view of the circuit interrupter shown inFigs. 1 and 2, and Fig.4: is a fragmentary front view, partially in elevation and partially in section, of a circuit interrupter embodying a modified form of my invention.

A conductor 1, which carries a relatively large amount of current, is connected to a two-pole circuit interrupter 2. The circuit interrupter 2 comprises two similar switching members or poles 3 and l which are con nected in parallel relation to transmit proportional parts of the current traversing the conductor 1. The switch member 3, comprises two terminal members 5 and 6, stationary contact members 7, movable contact members 9 anda bridging member 11. The switch member 4; comprises terminal members 12 and 13, to the lower ends of which are attached stationary contact members 14 and movable contact members 15 which are connected by a bridging member 16, substantially the same as was described with respect: to the switching member 3. The bridging members 11 and 16 are connected together by an insulating member 17 to which is attached an operating rod 18, for purposes hereinafter set forth. The stationary and movable contact members of the respective switching members 3 and 4 are immersed in an oil-containing receptacle 19.

A magnetizable member 20 is disposed around the terminals 5 and 12 in such manner that any flux which may be induced in the same by the current traversing the switching device 3 will be counterbalanced by the flux which will be induced in the same by the current traversing the switching device t, if these two currents are of the same value. v

If the characteristics of the switching devices 3 and 4 are not the same with respect to relative impedances, the difference in eurrent which will ordinarily traverse the two devices will induce a flux in the device 20 that will induce a voltage in the circuit carrying the lower current which will tend to equalize the impedance of the two circuits and also the currents traversing the same. It'will be noted that the device 20 consists substantially of a magnetizable member of the shape of a figure 8, the arms that'cross,

however, not being in contact with each other.

The rod 18 may be so connected to an opcrating mechanism (not shown) and a tripping device (not shown) as to automatically trip when predetermined overloads occur in the conductor 1. As many switching units as are desired may be placed in parallel,

either in the same receptacle or in separate receptacles, to carry the current. The essential feature of the device is that the terminals of each of the switching devices shall be so inductively connected to each of the other terminals as to equalize the currents normally traversing the parallel circuits.

Referring now particularly to Fig. 4 of the drawings, instead of disposing the magnetizable member 20 upon the terminals 5 and 12, I dispose a magnetizable core member 21 on the terminal 12 and a magnetizable core member 22 on the terminal 5. Two coils 23 and 24 are respectively disposed around the magnetizable core members 21 and 22, as will be seen from the drawings. The terminals of the coils 23 and 24 are connected together in such manner that the normal currents traversing them are opposed in direction, at any instant.

If the impedances of the two parallel paths through the circuit interrupter are of different values, the currents which traverse the same will not ordinarily be equal. If the path through the terminals 12 and 13 is of relatively higher impedance than the path through the terminals 5 and 6, more current will ordinarily traverse the path through the terminals 5 and 6. If the device shown in Fig. 4 is employed, a flux will be induced in each magnetizable member that is proportional to the current traversing the terminal around which it is disposed. The fluxes will induce voltages in the respective coils 23 and 24 and, since the coils are connected to form a closed circuit, a current will tend to flow from each coil that is proportional to the current traversing its terminal. Since the coils are connected to oppose each other, only a resultant current will actually traverse the same. The resultant current will induce a flux in the magnetizable core 22 which will increase the current traversing the path through the terminals 5 and 6. The currents through the two paths are thus balanced.

Similar magnetizable cores and coils may be disposed upon the terminals 6 and 13, as

was described with respect to the Figs. 1, 2 and 3.

While I have described my invention with respect to particular structures, it is not so limited, but is capable of various modifications within the scope of the appended claims.

I claim as my invention:

1. The combination with a plurality of parallel-connected circuit interrupters, of a closed-magnetic-circuit magnetizable member surrounding the conductors of the interrupters for equalizing the currents traversing the same.

2. The combination with a plurality of parallel-connected circuit interrupters, of a magnetizable member having substantially the shape of the figure eight for magnetically connecting adjacent interrupters to equalize the currents traversing the same.

3. The combination with two circuit interrupters operatively connected in parallel, of a closed-magnetic-circuit magnetizable member surrounding similar conductors of the interrupter for equalizing the currents traversing the same.

4. The combination with a plurality of circuit interrupters operatively connected in parallel, of a closed-magnetic-circuit magnetizable member surrounding one of the conductors of each circuit interrupter for equalizing the currents traversing the same.

5. In a double-pole parallel-connected circuit interrupter, the combination with 006 crating contact members and terminal bus ings for the circuit interrupter conductors, of a magnetizable member having substantially the shape of the figure eight surrounding the terminal bushings for equalizing the currents traversing the conductors and the contact members.

In testimony whereof, I have hereunto subscribed my name this 22nd day of May,

KARL C. RANDALL. Witnesses:

BERTRAND P. Rown, B. B. Hnms.

Copies of this patent may be obtained for five cents each, by addressing the "Commissioner of Patents,

Washington, I). O. 

